Exploring the Cu‐In‐S System under Solvothermal Conditions near the Composition CuIn5S8

Solvothermal syntheses of copper‐indium‐sulfides performed with different Cu:In:S ratios afforded crystallization of nanocrystalline Cu‐In‐S phases with compositions close to CuInS₂, CuIn₃S₅, and CuIn₇S₁₁. Each sample shows a different and distinguishable morphology. The minority component CuInS₂ with wurtzite‐type structure crystallizes as thin plates, which are preferably stacked parallel to black stacks. The component with composition CuIn₃S₅ forms isolated few nm thin layers being arranged like the petals of a flower growing from a common point. Finally, red CuIn₇S₁₁ is obtained as nanobelts with individual diameters of about 20 nm and lengths up to more than 1 μm. According to electron diffraction patterns and X‐ray diffractometry the structures of CuIn₃S₅ and CuIn₇S₁₁ cannot be assigned to known bulk phases of the Cu‐In‐S system, however first structure models are proposed.